LTC1174-3.3_15 Datasheet, PDF (6/20 Pages) Linear Technology – High Efficiency Step-Down and Inverting DC/DC Converter

LTC1174
LTC1174-3.3/LTC1174-5
PI FU CTIO S
V_OUT (V_FB) (Pin 1): For the LTC1174, this pin connects to the
main voltage comparator’s input. On the LTC1174-3.3 and
LTC1174-5 this pin goes to an internal resistive divider
which sets the output voltage.
LB_OUT (Pin 2): Open Drain of an N-Channel Pull-Down. This
pin will sink current when Pin 3 (LB_IN) goes below 1.25V.
During shutdown the state of this pin is indeterminate.
LB_IN (Pin 3): The “–” Input of the Low-Battery Voltage
Comparator. The “+” input is connected to a reference
voltage of 1.25V.
GND (Pin 4): Ground Pin.
SW(Pin5): Drain of the P-Channel MOSFET Switch. Cathode
of Schottky diode must be closely connected to this pin.
V_IN (Pin 6): Input Supply Voltage. It must be decoupled
close to ground Pin 4.
I_PGM (Pin 7): Selects the Current Limit of the P-Channel
Switch. With I_PGM = V_IN, the current trip point is 600mA and
with I_PGM = 0V, the current trip value is reduced to 340mA.
SHUTDOWN (Pin 8): Pulling this pin to ground keeps the
internal switch off and puts the LTC1174 in micropower
shutdown.
W
FU CTIO AL DIAGRA _{(Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)}
V_IN
6
+
V_TH2
A5
–
SLEEP
V_LIM1
V_LIM2
I_PGM
7
R_SENSE
0.1Ω
A2
g_mV_FB
LB_OUT 2
GND 4
–
A4
C_T
+
V_TH1
LB_IN
3
A3
RESET
Q
SET
1.25V
REFERENCE
SHUTDOWN
8
* R1 = 51k FOR LTC1174-3.3
R1 = 93.5k FOR LTC1174-5
V_OUT (V_FB)
1
5
× SW
R1*
V_FB
A1
31.5k
1174 BD
1174fe
6